An international rights group says there are major gaps in the oil productions figures published by the Sudanese government and the main Chinese oil company operating in the country.
Britain-based Global Witness says the oil production figures published by the Chinese National Petroleum Company are 12 percent higher than those published by the Sudanese government.
Rosie Sharpe, from Global Witness, says that is a difference of 12 million barrels of oil, worth $370 million.
Under a peace deal between the north and south of Sudan, oil revenues are supposed to be shared between the two regions.
Sharpe says this makes it important that oil revenues are reported correctly. "That raises the suspicion that the government might be under-reporting the amount of oil that is produced and therefore underpaying the government of the South the amount of money that it owes in oil revenues." she said.
Sharpe says it is impossible to know if the government has misreported the figure. "You do not know which of the figures is correct, perhaps the government's one is the correct figure. What it does tell you, however, is that no-one can know for sure at the moment how much oil Sudan produces and therefore no-one can know for sure at the moment how much money the South should be getting," she said.
Global Witness first highlighted the gap in oil data in a report published six months ago and at the time, says Sharpe, authorities in both north and south Sudan said they would address the inconsistencies by conducting an audit. Sharpe says that audit has yet to take place.
But she says correct records are fundamental for stability in Sudan. "The oil money has been the glue that has held the two sides together for the past five years, that is why it is important that we get it right, it is the figures that underlie that power sharing," said Sharpe.
Sudan has undergone two north-south civil wars since independence in 1956. In 2005 the government and rebels signed a peace deal giving a high level of autonomy to the south.
A referendum is set to take place in the South in 2011 to decide if the region will become independent.
Sharpe says if another wealth-sharing agreement is made at that time trust will be crucial.
According to the International Monetary Fund, oil represented 95 percent of export revenues and 60 percent of government revenues in Sudan in 2008.